A salesman, who had completed a trip earlier than expected, left his wife a message on their answering machine. When he got home, he found his wife in bed with another man. Being a non-violent type, he went to his father-in-law and told him what happened. "I'm sure there must be an explanation," his father-in-law assured him.

The next day, the husband came back to the father-in-law smiling. "I knew it! I knew there was an explanation," he said. "She forgot to check her phone messages."